1. Field of the Invention
The invention concerns an axle suspension for air-suspended utility vehicles and the like in which the vehicle chassis is supported by a pneumatic spring for the support and guidance of pneumatic spring bellows. The bellows are connected by means of an upper mounting plate with the vehicle chassis resting on it, and e.g., by means of a bottom plate with the top of a plunger piston which is e.g. braced on a spring leaf assembly.
2. Description of Related Art
Such an axle suspension is for example known from DE 42 01 629 C1. The known arrangement features at least one spring leaf assembly on either side of the perpendicular longitudinal center plane of the vehicle. The spring leaf assembly is hinged at its front end to a chassis-mounted bearing and at a distance from it rigidly connected with an axle housing and at its rear end supports the vehicle chassis by means of the pneumatic spring. The purpose of this axle suspension was to make the greatest possible axle spring travel of up to 450 mm possible. With this known method this purpose is achieved by the fact that the geometric central axis of the plunger piston and in essence the plunger piston casing as seen from the point of support have a concave curvature. The resultant more favorable motion sequence achieves that the critical distance of the upper inner comer of the spring is configured as a plunger piston assembly, is preferably cylindrical and has a plunger piston intended plunger piston from the pneumatic spring bellows increases. This results in greater axle spring travel.
In addition, it can be seen from a comparison of the characteristic curves of the plunger piston (axle load over axle spring travel) that with the use of such curved plunger pistons at equal bellows pressure, the axle load is held over a longer axle spring excursion than with air suspensions with a straight plunger piston. This guarantees safe raising of a loaded vehicle.
It has become clear that, for example, for the use of axle suspensions for vehicles in interchange operations, i.e. for instance for trailers/semitrailers used in these operations there is a need for still greater axle spring travel in order to be able to handle quite different parking heights which vary by more than 450 mm.
The purpose of the present invention is to meet this requirement for an axle suspension of a similar type in a simple manner.
The purpose is essentially achieved by the fact that there is either at the edge of the mounting plate a downward pointing collar of a predetermined height and top end of the pneumatic spring bellows is attached to the bottom end of the collar at a corresponding distance from the primary plane of extension of the mounting plate, or that the pneumatic spring bellows are attached to the peripheral edge of the mounting plate itself and are surrounded below the mounting plate by at least one collar of a predetermined height (7).
The first alternative achieves that the maximum travel of the pneumatic spring bellows when these are pressurized is extended by 2xc3x97 the height of the collar if at equal plunger piston length, pneumatic spring bellows lengthened by 1xc3x97 the height of the collar are used, and by 1xc3x97 the height of the collar if with a plunger piston shortened by 1xc3x97 the height of the collar, the same pneumatic spring bellows are used. This can be explained by the fact that when the pneumatic spring bellows are depressurized, as happens when the vehicle chassis is lowered to its lowest level, the top part of the bellows rolls over the external peripheral surface of the collar because of the existing geometric ratios and so forms an additional fold there. Compared to a conventional pneumatic spring it is in this way possible to achieve either a decreased blocking length or an increased bellows deflection, and therefore axle spring travel.
The second alternative has the advantage that the pneumatic spring bellows can be attached to the unchanged mounting plate as before and with the use of the same plunger piston and therefore equal blocking height, but with pneumatic spring bellows lengthened by 2xc3x97 the height of the collar, the maximum axle spring travel is increased by 2xc3x97 the height of the collar, and by 1xc3x97 the height of the collar, if with a plunger piston shortened by 1xc3x97 the height of the collar, pneumatic spring bellows lengthened by 1xc3x97 the height of the collar are used.
In a further development of the inventive thought, the collar like the adjacent area of the pneumatic spring bellows is of a more or less circular and cylindrical design, e.g. a separate hoop. This contributes to easy manufacture, low-weight construction and reliable operation.
It is particularly advantageous for the operation of the novel plunger piston configuration if the collar mounted on the mounting plate has a diameter which basically matches the diameter of the top area of the pneumatic spring bellows. This enables the top edge of the pneumatic spring bellows during the lowering of the vehicle chassis to slide comfortably over the collar to form a double-layer fold and to unroll without problem from the collar when the vehicle chassis is raised.
Advantageously, in the first alternative of the invention, the collar which like the mounting plate itself is, for example, made of steel plate, is connected at its bottom end to the top end of the pneumatic spring bellows by means of a bead.
In the second alternative the peripheral edge of the mounting plate is advantageously connected with the top end of the pneumatic spring bellows by means of a bead which can be done without difficulty.
In the first alternative the collar can be connected rigidly, e.g. in one piece, with the mounting plate.
In the second alternative a connection of the at least single collar with the mounting plate is not necessary. The collar is rather situated on the external circumference of the pneumatic spring bellows where it can, for example, rest against the bead of the mounting plate edge and may there, for example, also be adapted in its geometric shape to the bead. However, it may also sit at a suitable distance from the mounting plate on the circumference of the pneumatic spring bellows.
To avoid particularly in the first alternative accumulation of dirt in the space between the fold of the pneumatic spring bellows forming near the collar and the external circumference of the collar connected to the mounting plate or resting against it when the vehicle chassis is fully or partially lowered, the external circumference of the collar may be surrounded by a covering that is closed at the top and whereby there is a space between collar and covering. The cover is designed in such a way that the forming of the fold at the top edge of the pneumatic spring bellows during lowering of the vehicle chassis takes place in the space between the covering and the collar.
As a further development of this thought the covering may also consist of a flexible material, may rest with its bottom peripheral edge against the exterior of the pneumatic spring bellows and be taken along by them so that the accumulation of dirt as referred to above is avoided.
To prevent damage of the pneumatic spring bellows at the edges of the collar, the latter may be rounded.
It is also possible to utilize the folding of the pneumatic spring bellows for the reduction of the blocking height and the increase of the maximum pneumatic spring bellows travel for an axle suspension of this type or an axle suspension of the type discussed previously, if a second set of pneumatic spring bellows is arranged in the plunger piston with a second plunger piston at the bottom end of this second set of pneumatic spring bellows.
In this case the second set of pneumatic spring bellows can be connected to the top of the plunger piston by means of a second mounting plate.